1. Technical Field
The present invention relates in general to sensors used in hard disk drives and, in particular, to an improved system, method, and apparatus for configuring giant magneto-resistance sensors with current-perpendicular-to-the-plane apertures.
2. Description of the Related Art
Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm). Hard disk drives have several different typical standard sizes or formats, including server, desktop, mobile (2.5 and 1.8 inches) and microdrive.
A typical HDD also uses an actuator assembly to move magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
A slider is typically formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.
In HDDs, giant magneto-resistance (GMR) sensors having a current-perpendicular-to-the-plane (CPP) configuration offer a number of advantages over current-parallel-to-the-plane (CIP) GMR sensors. In particular, the effective width of CIP sensors, which contributes to the GMR signal, cannot easily be scaled to less than 75 nm, which is necessary for areal densities greater than about 200 Gb/in2. In contrast, CPP sensors can be scaled to less than 75 nm without degradation in the GMR signal. However, one problem with all-metallic CPP sensors is very low resistance, which leads to either low voltage output or very high current. Low voltage output can cause problems with low head signal-to-noise ratio (SNR), especially when the CPP resistance is as small as the series lead resistance, whereas high current can lead to problems with magnetic torque noise, which also degrades head SNR. Thus, an improved solution that overcomes these problems would be desirable.